Geological Evidence for the Earliest Appearance of Hominins in Indonesia

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Until the end of Tertiary period (Pliocene), almost all Indonesian regions were still occupied by a marine environment. Tectonics and glacioeustatic changes took place during the Pleistocene to form the Indonesian Archipelago, including the emergent lands known as Sunda Land and the Sahul Shelf. The Sunda Land connected Asia mainland with the islands of Sumatra, Java and Kalimantan. It also acted as a land bridge and migration route for Homo erectus and vertebrate faunas from the Asia mainland to Java. In the Pleistocene, the sedimentations in Indonesian regions occurred mostly in non-marine environments: lakes and rivers (sometimes with marine influences) which are favorable for hominin and vertebrate occupations. The first arrival of vertebrate faunas from Asia to Indonesia through the Sunda Land at the end of the Late Pliocene and later on was followed by arrival of the early hominin – Homo erectus paleojavanicus (Meganthropus paleojavanicus) to Java in the Early Pleistocene (1.6–1.0 Ma). During the Middle to Late Pleistocene (1.0–0.125 Ma) there existed another hominin in Java as indicated by the presence of Homo erectus ngandongensis/soloensis. Recently, hominin fossils have also been discovered in eastern Indonesia, at Liang Bua, Flores island and are attributed to Homo floresiensis (orang pendek – pygmy people) dated as 12,000 BP or the end of Late Pleistocene probably coexistant with Homo sapiens. The very important site of hominin and vertebrate fossils in Indonesia and in Java is the Sangiran Dome. More than 152 fossils of Homo erectus in Indonesia are found in the Sangiran Dome, from Early Pleistocene deposits of the Sangiran Formation to Middle Pleistocene sediments of the Bapang Formation. These represent more than 77% of the total hominin specimens found in Java. The fossils represent an early human occupation since Sunda emerged from the Java Sea. Therefore, in the Quaternary, Java Island is the home for hominins in Southeast Asia. The human fossil Homo erectus and the vertebrate fossils found in Quaternary sediments in Java are very important for understanding human evolution in Indonesia and Southeast Asia and the initial expansion of hominins out of Africa.